In general, when it is intended to park a vehicle with a driver getting off, movement of the vehicle is restricted by actuating a parking brake system.
As for such a parking brake, in general, an equalizer equally distributes force applied to parking cables pulled by a parking brake lever to brakes mounted to wheels and the brakes restrict the wheels and prevent motion of a vehicle accordingly.
When a driver brakes wheel by operating a parking brake lever as described above, the driver had to manually operate a parking brake lever every time for parking-braking, so that it was inconvenient for drivers. Further, sometimes drivers forgot it and it is followed by danger of an accident.
For this reason, electric parking brake systems that are actuated by a motor for parking-braking and keep the braking safely to get rid of inconvenience in manual parking brakes have been used. In such an electric parking brake system, in general, when a driver pushes an operating switch to actuate a motor, as the motor rotates and pulls parking cables, equal braking force is applied to each wheel through an equalizer.
Further, such an electric parking brake system necessarily requires to measure tension acting in parking cables pulled by a motor, so that, in general, force due to compression and expansion of a spring is measured and locking of the parking cables is maintained and required driving force of the motor is controlled more accurately through the measured force.
According to such an electric parking brake system, in general, a motor that generates power, a gear box that converts the power into motion, and a screw rod that pulls parking cables are formed into an integral module, which is mounted to the trunk or the rear frame and a driver actuates it by operating an operating switch after getting off a vehicle.
Further, it is a tendency to improve such electric parking brake systems into as small size as: possible to provide convenience more in mounting and in order not to cause structural modifications for portions to mount due to the characteristics for mounting them to a real vehicle, because a module for generating power and converting motional direction is individually manufactured and then mounted a vehicle.
It is an object of the invention to provide a small-sized module for an electric parking brake system by efficiently integrating components for generating power, converting motional direction, and operating parking cables into a module, and improve productivity of the module by forming a housing box that forms the whole external shape of the module into an integral unit through injection molding.
It is another object of the invention to balance load of components mounted in a module housing box formed into an integral unit by injection molding and efficiently distribute and absorb vibration in the operation.
It is another object of the invention to provide an actuator that does not require a particular structural design for increasing durability of a housing box by stopping linear motional force from interrupting rotational motion when rotational power is converted into a for linear motion for pulling parking cables in a module.
It is another object of the invention to increase flexibility in laying-out in mounting a module as compared with modules using two cables by connecting parking cables through one cable to a linear motional member in a module.